Stars

Two objects in the Epsilon Indi system at the limit between star and brown dwarf

An article published in the journal “The Astrophysical Journal” describes a research on the brown dwarfs in the Epsilon Indi system in connection with the mass limits for this type of objects. A team of researchers combined the data obtained from various observations to re-estimate the two brown dwarfs masses, which were found to be 75.0 ± 0.82 and 70.1 ± 0.68 times the mass of the planet Jupiter. These are much higher masses than previous estimates and at least the largest one has a mass that according to the theoretical models is that of a star offering new information to understand where are the limits between these objects.

The images captured by TESS (NASA/MIT/TESS)

NASA has published a series of images captured by its TESS space telescope’s cameras. These are the first scientific images, that in jargon are called the first light, obtained on August 7, 2018 after the instrument testing period and show the southern sky. The images portray an amount of stars and other objects among which systems where exoplanets were already found. However, the main goal is to discover new exoplanets.

A possible pulsar formed after a long-duration supernova

An article published in the “Astrophysical Journal Letters” describes a study on the supernova Sn 2012au. Sometimes supernovae remain bright for a long time if the remnants of the explosion collide with hydrogen layers, but Dan Milisavljevic of Purdue University wondered if this could happen without any interaction of that kind. His team studied Sn 2012au concluding that after the supernova a neutron star of the pulsar type was formed with a rotation and a magnetic field sufficient to create a cloud of gas around it, called in jargon a pulsar wind nebula.

A ring galaxy with a lot of ultraluminous X-ray sources

An article published in the “Astrophysical Journal” describes the detection of a series of X-ray sources in the ring of the galaxy AM 0644-741. A team of researchers led by Anna Wolter from INAF-Osservatorio Astronomico di Brera, Italy, used observations from NASA’s Chandra X-ray Observatory to discover those ultraluminous sources concluding that the ring containing them consists of binary systems that include black holes or neutron stars and that the ring formed following a collision between galaxies.

A relativistic jet after the kilonova

An article published in the journal “Nature” describes the observations of a relativistic jet that followed the merger between two neutron stars discovered in August 2017, the first case of an event detected and studied in both electromagnetic and gravitational waves. A team of researchers used the precise measurements made with some radio telescopes to establish that a narrow jet of particles was emitted at a speed close to that of light after the event.